The present invention relates to the field of aircraft deicing, and more particularly, the present invention relates to an apparatus and method for deicing. aircraft using forced air from a compact, lightweight compressor unit.
Some deicing systems and methods used for deicing snow and ice-covered aircraft surfaces use an apparatus that sprays large quantities of deicing fluids onto the aircraft surfaces. Typically, this has been accomplished by spraying a heated antifreeze fluid (e.g., a glycol and water mixture) onto the iced surfaces of the aircraft, together with a large quantity of compressed air. An example includes the system disclosed in U.S. Pat. No. 5,244,168, the disclosure of which is incorporated herein by reference in its entirety, where a nozzle mixes pressurized air and deicing fluid to provide a spray pattern for application to the aircraft to deice the aircraft.
Other systems separate the glycol and water mixture from the compressed air and include a separate nozzle for discharging compressed air by providing a forced air deicing system having a powerful compressed air source. Typically, these systems include a vehicle frame, such as the chassis of a truck, having a boom with one end mounted on the vehicle frame and a free end. An operator cab is positioned at the free end of the boom and a deicer air jet nozzle is connected at the free end of the boom, typically mounted on the operator cab for operator control.
Many of these systems use very powerful jet engine air start units. The air exits the nozzle at a temperature of 300 degrees F to 400 degrees F above ambient. As a result, some of the ice and snow is melted and can migrate into crevices on the aircraft. The aircraft acts as a heat sink because the large mass of the aircraft remains at subfreezing temperatures. Thus, sensitive sensors and critical trailing edge flaps may become frozen and ineffective.
Typically, this type of compressor is capable of 300 to 500 horsepower and provides 300 to 400 pounds per minute of compressed air. The units are very inefficient, producing unnecessary hot air and excessive noise. Additionally, these systems are very heavy and must be positioned near the vehicle frame, a long distance from the operator cab carrying an air jet nozzle. As a result, long tubes must extend from the vehicle frame along the boom to the operator cab where the nozzles are located. These long runs from the compressor can cause thermodynamic and pneumatic deficiencies.
Also, any system that injects fluid at high pressure into the air stream has a drawback because the fluid could act as a cutting medium and damage aircraft surfaces. Therefore, it is essential in some instances to keep a great distance from the aircraft to avoid damaging the aircraft with the high pressure fluid, thus making the forced air system ineffective.
Previous systems and methods for deicing aircraft have attempted to overcome many of the aforementioned problems. For example, Giroux, xe2x80x9cHot Air Blast System: An Alternative to Heated Glycol Deicingxe2x80x9d (Jun. 12, 1997), which is incorporated herein by reference, discloses a system for removing accumulations of snow prior to deicing with heated glycol. The Giroux publication, however, does not teach or suggest a deicing system capable of using both hot air and limited quantities of deicing fluid. Moreover, Giroux does not teach or suggest using a compact, lightweight compressor unit and actually teaches away from using a turbocharger-based deicing system.
In addition, Allied Signal Aerospace, xe2x80x9cAllied Signal""s Augmented Forced-Air Deicing (AFAD)xe2x80x9d (Oct. 22, 1996), which is incorporated herein by reference, discloses an Augmented Forced-Air Deicing system. The Allied Signal publication, however, does not teach or suggest using a compact, lightweight compressor unit. Moreover, the Allied Signal publication suggests a compressor unit mounted on a vehicle at the base of a deicing boom and actually teaches away from a compressor unit mounted proximate to an air jet nozzle.
Furthermore, Warnock, U.S. Pat. No. 4,423,980 (Jan. 3, 1984), which is incorporated herein by reference, discloses a truck-mounted apparatus for repairing asphalt. The Warnock patent, however, does not teach or suggest a system for deicing aircraft. More specifically, the Warnock patent does not suggest a deicing system having a compact, lightweight compressor unit mounted proximate to an air jet nozzle.
Peppard, U.S. Pat. No. 5,134,266 (Jul. 28, 1992), which is incorporated herein by reference, discloses a mobile deicing apparatus for melting accumulated ice from aircraft surfaces. The Peppard patent, however, does not teach or suggest a deicing system having a compact, light weight compressor unit mounted proximate to an air jet nozzle.
Moreover, Numbers et al., U.S. Pat. No. 6,250,588 (Jun. 26, 2001), which is incorporated herein by reference, discloses a forced air deicing and washing system attached to the distal end of a boom. Numbers was filed after the priority date of this application. Numbers does not teach or suggest a deicing system having a compact, light weight compressor unit with a high power-to-weight ratio, as disclosed in the present invention.
Accordingly, there is a significant need for a system and method for deicing that: (1) effectively removes ice and snow from critical equipment surfaces; (2) with improved efficiency by placing a lightweight air source proximate to the air nozzle; (3) with a high power-to-weight ratio; (4) at lower cost; and (5) while reducing the amount of hazardous and costly deicing fluids used.
Recently, Assignee""s U.S. Pat. No. 6,045,092, to which the present application claims priority, was the subject of litigation. Opponents of the ""092 patent argued that its scope was limited to a deicer system having a compressor unit mounted directly on the boom in the location shown in FIG. 1. Without prejudice to Assignee""s rights, Assignee believes that the invention disclosed in the ""092 patent is much broader than this narrow interpretation of the claims. Because of a concern that the claims of the ""092 patent were unclear and might arguably be limited to a scope of protection that is less than that to which Assignee was entitled, Assignee disclaimed the claims of the ""092 patent and filed the present application.
Although the ""092 patent discloses, in a preferred embodiment, a deicing system having a compressor unit that can be mounted on a boom (see Col. 3, II. 39-42), the placement of the compressor unit is not limited to this location in Assignee""s priority documents. Rather, the language of the ""092 patent and priority documents expressly distinguish over prior systems having large compressors located on the vehicle frame (see col. 4, II. 13-18). As such, the ""092 patent discloses a deicing system having a lightweight compressor unit located anywhere on the boom side of the bearing that attaches the boom to the vehicle frame. Numerous locations for the compressor unit on the boom side of the bearing, as well as other variations and modifications that fall within the scope of the ""092 patent, will be apparent to persons of ordinary skill in the art. Thus, it is expressly intended that the present invention resolve any ambiguity regarding placement of the compressor and include these variations and modifications, provided they come within the scope of the appended claims and their equivalents.
It is therefore an object of the present invention to provide a system and method for deicing aircraft using a compact, lightweight air source that is not limited to being mounted on the vehicle frame.
It is another object of the present invention to provide a system and method for deicing aircraft using a compact, lightweight air source located proximate to a deicer air jet nozzle.
It is still another object of the present invention to provide an apparatus and method for deicing aircraft that uses forced air discharge that is efficient and uses a compressor unit that is lightweight, but generates an air discharge from a deicer air jet nozzle that is appropriate for deicing aircraft under frigid conditions, but also does not discharge at temperatures substantially above ambient temperature.
In accordance with the present invention, an apparatus and method for deicing aircraft now allows a compressor unit to be mounted on the vehicle boom by the use of a centrifugal compressor, such as the type of compressor commonly used when supercharging internal combustion engines. This type of compressor preferably is directly connected to a motor output, which in a preferred aspect of the invention is a hydraulic motor via a transmission, such as a belt, and in a preferred aspect, a drive gear unit. The centrifugal compressor includes an impeller and outlet as is normal with many of the superchargers used in automobile vehicle engines. The apparatus includes a vehicle frame and a boom having one end mounted on the vehicle frame and a free end. The compressor unit preferably is located proximate to the free end and a deicer air jet nozzle is connected at the free end of the boom and operatively coupled to the air outlet of the centrifugal compressor for receiving air and discharging the air for a deicer application.
A hydraulic pump preferably is mounted on the vehicle frame and hydraulic feed lines extend from the hydraulic pump along the boom to the hydraulic motor for supplying hydraulic fluid under pressure to the hydraulic motor. The vehicle frame can typically include a vehicle engine, such as normal with a truck. A transmission is driven from the vehicle engine and interconnects the hydraulic pump for supplying power to the hydraulic motor.
A drive gear unit is preferably operatively connected between the centrifugal compressor and the hydraulic motor for stepping up the revolutions per minute of the centrifugal compressor relative to the output of the hydraulic motor. The drive gear unit is preferably a single increasing gear set located within the compressor. Alternatively, the drive gear unit is a set of two increasing gear sets for stepping up the revolutions per minute of the centrifugal compressor relative to the output of the hydraulic motor. The deicer air jet nozzle defines an axisymmetric contour having a converging portion. An example of such an air jet nozzle is disclosed in U.S. Pat. No. 5,755,404, the disclosure of which is incorporated herein by reference in its entirety.
Typically, a fluid nozzle is mounted on the deicer air jet nozzle. A source of deicing fluid could be mounted at the vehicle frame and a supply tube interconnects the source of deicing fluid in the fluid nozzle. A pump is operatively connected to the source and supply tube and pumps deicing fluid from the source of deicing fluid through the supply tube and fluid nozzle. Typically, if an aircraft contains much ice, the deicing fluid would he placed on the ice to aid in melting the ice. A pump, such as, for example, a centrifugal pump, can typically inject deicing fluid into the air stream at 100 to 200 PSIG. Any greater pressure could create problems with aircraft damage.
As will be apparent to persons of ordinary skill in the art, a compressor unit of the type disclosed in a preferred embodiment of the present invention typically weighs in the range of about 75 to about 110 pounds. Moreover, the size of the compressor unit according to one embodiment of the present invention is typically in the range of about 9 cubic feet to about 11 cubic feet. Furthermore, the compressor unit of the present invention typically has a power-to-weight ratio in the range of about 0.8 to about 1.6 horsepower/pound.
A method aspect is also disclosed and includes the steps of compressing air within a centrifugal compressor located on a vehicle boom by driving a motor coupled to the centrifugal compressor and discharging the air from a deicer air jet nozzle attached to the end of the vehicle boom such that air is forced outward from the deicer air jet nozzle at about 100 pounds per minute.